This invention relates to flame retardant compositions. More particularly it relates to flame retardants for polyurethane compositions especially rigid foams.
Polyurethanes are employed for example as rigid foams in commercial and residential buildings, as flexible foams in mattresses and furniture upholstery, and as coatings on wood furniture and flooring. To protect lives and property flame retardants are used to minimize combustion in polyurethane products alone or increasingly in combination.
Among the individual flame retardants for polyurethane products are alumina and other oxides as flame retardants and fillers, antimony compounds, both inorganic and organic halogen compounds particularly those containing chlorine and bromine, and compounds of phosphorus both organic and inorganic.
Increasingly, it has become attractive to experiment with employing combinations of flame retardants. This is particularly so for the combination of organophosphorus and organohalogen compounds in both rigid and flexible foams of polyurethanes.
In U.S. Pat. No. 4,194,068 Miller et al disclose a tripartite liquid flame retardant composition for cellular polyurethanes consisting of a bromohydrin or pentaerythritol, a polyhydric alcohol, and a sufficient amount of a flame retardant organophosphorus compound to render the mixture liquid at 25.degree. C.
In U.S. Pat. No. 4,025,470 Andres et al disclose a tripartite flame retardant composition for rigid polyurethane foams comprising an alcohol or polyol, a lactam and a phosphorus containing acid or ester. In the Andres patent rigid polyurethane foams are prepared from polyols and polyisocyanates. At column 3, line 67 it is disclosed in passing that the polyol may be substituted by halogen atoms.
In U.S. Pat. No. 3,826,762 Treadwell discloses a tripartite flame retardant system for polyurethane foams comprising an inert non-porous filler, a halogen source, and a phosphorus containing compound, almost invariably inorganic. In this disclosure the inert inorganic non-porous filler is coated with a mixture of the source of halogen and the phosphorus containing compound.
Thermoplastic polymers such as vinyl polymers, nylons, cellulosic resins, and polycarbonates may be protected by a synergistic mixture of a chlorinated hydrocarbon and a phosphinic acid according to the disclosure in U.S. Pat. No. 3,582,510.
Cellulose acetate laboratory specimens are rendered self-extinguishing when subjected to an Underwriters Laboratories burning test (UL 94) by inclusion of a plasticizing mixture of a trialkyl phosphate and an organic bromine compound, as disclosed in U.S. Pat. No. 3,515,565.
A principal object of this invention is to minimize the combustibility of polyurethane products by use of two flame retardants one containing halogen and the other containing phosphorus both flame retardants being organic in nature.
An additional object of the invention is to produce rigid polyurethane foams with reduced combustibility by the criterion of the ASTM E84 Surface Burning of Materials Test.
A further object of the invention is to provide a rigid polyurethane foam with low smoke density as measured by the ASTM E84 Smoke Density Test.
Still a further object of the invention is to provide more flexibility to the formulator of polyurethane products by providing separate sources of flame retardants containing organophosphorus and organochlorine or organobromine so that the phosphorus/halogen ratio may be varied.
Other objects of the invention will be apparent to those skilled in the art by inspection of the disclosure and Examples which follow.